There's A Copper Ring Inside My 9mmp Cases

[woodyblue]

After reloading some 9mmLuger cartridges with 124gr TMJ bullets and Ba9 powder (4.6gr) I found them to run at 300 m/s at 2.5m from the muzzle (using a Chrony).

Following a detailed observation of the spent cases I appreciated a bit too much fouling (soot) and the part where the bullet was inserted now looks copper colored. Sometimes there's even a partial or full ring where the base of the bullet was.

Considering that Ba9 powder is on pair with Vihta N330 as far as burning rate concerns (Ba9 it's on the low pressure side) and that speed wasn't all that high, what that copper residues are?

[Patrick Sweeney]

Copper colored powder residue? Can you scrape some out with a dental pick? Is it fused to the case, or just a deposited ring? Is it still there after you tumble clean your brass? We need more info.

[Bigbadaboom]

There may be a burr at the edge of your chamber.

[woodyblue]

Copper colored powder residue? Can you scrape some out with a dental pick? Is it fused to the case, or just a deposited ring? Is it still there after you tumble clean your brass? We need more info.

The powder residue (soot) is black, and there's a bit too much of it on the sidewalls of the cases. Mostly inside them.

The copper coloring is fused with the cases, it cannot be scraped or tumbled.

I assume the chamber is perfect. The gun is a S&W Target Champion 9mmP from their Custom Center. It has had around 2,000 rounds thru it.

Crimp diameter: 9.65mm

OAL: 28.70mm

Frontier bullets. TMJ, the soft ones.

[woodyblue]

While I don't have a capability for taking close pics I wanted to give it a try. The results aren't any good. Anyway, I preffer to upload those pics in case somebody finds them of interest.

The copper ring I was talking about can only be seen on picture D.jpg (lower left corner). In that pic appears as if it was black. That's because my inability to take close pictures.

[woodyblue]

Chronographed velocity. It's a 7-round string starting from a cold barrel: m/s

Lo 275.7

Hi 314.5

Av 299.2

ES 38.89 (14.11 %)

SD 12.72

After deducting the first three rounds (I consider them heating rounds) the maths are:

Lo 293.9

Hi 309.0

Av 301.9

ES 15.1 (5.14 %)

SD 6.5

Always in m/s.

The PF is 123 but I plan to use this load to improve marksmanship always in training.

The essay's weather was:

Temperature: 23 ºC

Humidity: 39 %

Pressure: 942 hPa

Radiation: 581 W/m2

All bullets measured .3555" diameter (9.03mm) and weighted (grains):

Av 123.7

n 20

SD 0.5

Lo 122.9

Hi 124.6

ES 1.7 (1.38 %)

From a 20-bullet sample.

I don't know what I can add besides all the above collected data so I'm waiting for your comments (about that copper coloring inside the cases).

Edited May 26, 2006 by woodyblue